KS-Validation

Validation

Form Validation

Provide valuable, actionable feedback to your users with HTML5 form validation, via browser default behaviors or custom styles and JavaScript.

How it works

Here is how form validation works with Bootstrap:
HTML form validation is applied via CSS two pseudo-classes, `:invalid` and `:valid`. It applies to `<input>`, `<select>`, and `<textarea>` elements.
Bootstrap scopes the `:invalid` and `:valid` styles to parent `.was-validated` class, usually applied to the `<form>`. Otherwise, any required field without a value shows up as invalid on page load. This way, you may choose when to activate them (typically after form submission is attempted).
To reset the appearance of the form (for instance, in the case of dynamic form submissions using AJAX), remove the `.was-validated` class from the `<form>` again after submission.
As a fallback, `.is-invalid` and `.is-valid` classes may be used instead of the pseudo-classes for server-side validation. They do not require a `.was-validated` parent class.
Due to constraints in how CSS works, we cannot (at present) apply styles to a `<label>` that comes before a form control in the DOM without the help of custom JavaScript.
All modern browsers support the constraint validation API, a series of JavaScript methods for validating form controls.
Feedback messages may utilize the browser defaults (different for each browser, and unstylable via CSS) or our custom feedback styles with additional HTML and CSS.
You may provide custom validity messages with `setCustomValidity` in JavaScript.
With that in mind, consider the following demos for our custom form validation styles, optional server-side classes, and browser defaults.

Custom styles

For custom Bootstrap form validation messages, you will need to add the `novalidate` boolean attribute to your `<form>`. This disables the browser default feedback tooltips, but still provides access to the form validation APIs in JavaScript. Try to submit the form below; our JavaScript will intercept the submit button and relay feedback to you. When attempting to submit, you will see the `:invalid` and `:valid` styles applied to your form controls.
Custom feedback styles apply custom colors, borders, focus styles, and background icons to better communicate feedback. Background icons for `<select>`s are only available with `.form-select`, and not `.form-control`.

Browser defaults

Not interested in custom validation feedback messages or writing JavaScript to change form behaviors? All good, you can use the browser defaults. Try submitting the form below. Depending on your browser and OS, you will see a slightly different style of feedback.
While these feedback styles cannot be styled with CSS, you can still customize the feedback text through JavaScript.

Server side

We recommend using client-side validation, but in case you require server-side validation, you can indicate invalid and valid form fields with `.is-invalid` and `.is-valid`. Note that `.invalid-feedback` is also supported with these classes.
For invalid fields, ensure that the invalid feedback/error message is associated with the relevant form field using `aria-describedby` (noting that this attribute allows more than one `id` to be referenced, in case the field already points to additional form text).
To fix issues with border radii, input groups require an additional `.has-validation` class.

Example:

                                    <html>

<head>
    <!-- CSS only -->
    <link href="https://cdn.jsdelivr.net/npm/bootstrap@5.0.1/dist/css/bootstrap.min.css" rel="stylesheet" integrity="sha384-+0n0xVW2eSR5OomGNYDnhzAbDsOXxcvSN1TPprVMTNDbiYZCxYbOOl7+AMvyTG2x" crossorigin="anonymous">
</head>

<body>
    <form class="row g-3 needs-validation" novalidate>
        <div class="col-md-4">
            <label for="validationCustom01" class="form-label">First name</label>
            <input type="text" class="form-control" id="validationCustom01" value="Mark" required>
            <div class="valid-feedback">
                Looks good!
            </div>
        </div>
        <div class="col-md-4">
            <label for="validationCustom02" class="form-label">Last name</label>
            <input type="text" class="form-control" id="validationCustom02" value="Otto" required>
            <div class="valid-feedback">
                Looks good!
            </div>
        </div>
        <div class="col-md-4">
            <label for="validationCustomUsername" class="form-label">Username</label>
            <div class="input-group has-validation">
                <span class="input-group-text" id="inputGroupPrepend">@</span>
                <input type="text" class="form-control" id="validationCustomUsername" aria-describedby="inputGroupPrepend" required>
                <div class="invalid-feedback">
                    Please choose a username.
                </div>
            </div>
        </div>
        <div class="col-md-6">
            <label for="validationCustom03" class="form-label">City</label>
            <input type="text" class="form-control" id="validationCustom03" required>
            <div class="invalid-feedback">
                Please provide a valid city.
            </div>
        </div>
        <div class="col-md-3">
            <label for="validationCustom04" class="form-label">State</label>
            <select class="form-select" id="validationCustom04" required>
                <option selected disabled value="">Choose...</option>
                <option>...</option>
            </select>
            <div class="invalid-feedback">
                Please select a valid state.
            </div>
        </div>
        <div class="col-md-3">
            <label for="validationCustom05" class="form-label">Zip</label>
            <input type="text" class="form-control" id="validationCustom05" required>
            <div class="invalid-feedback">
                Please provide a valid zip.
            </div>
        </div>
        <div class="col-12">
            <div class="form-check">
                <input class="form-check-input" type="checkbox" value="" id="invalidCheck" required>
                <label class="form-check-label" for="invalidCheck">
                    Agree to terms and conditions
                </label>
                <div class="invalid-feedback">
                    You must agree before submitting.
                </div>
            </div>
        </div>
        <div class="col-12">
            <button class="btn btn-primary" type="submit">Submit form</button>
        </div>
    </form>

    <script>
        // Example starter JavaScript for disabling form submissions if there are invalid fields
        (function() {
            'use strict'

            // Fetch all the forms we want to apply custom Bootstrap validation styles to
            var forms = document.querySelectorAll('.needs-validation')

            // Loop over them and prevent submission
            Array.prototype.slice.call(forms)
                .forEach(function(form) {
                    form.addEventListener('submit', function(event) {
                        if (!form.checkValidity()) {
                            event.preventDefault()
                            event.stopPropagation()
                        }

                        form.classList.add('was-validated')
                    }, false)
                })
        })()

    </script>
</body>

</html>

Output:

First name

Looks good!

Last name

Looks good!

Username

Please choose a username.

City

Please provide a valid city.

State

Please select a valid state.

Zip

Please provide a valid zip.

Agree to terms and conditions

You must agree before submitting.

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Validation

Form Validation

How it works

Custom styles

Browser defaults

Server side

Example:

Output:

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Validation

Form Validation

How it works

Custom styles

Browser defaults

Server side

Example:

Output:

Do you Know?

Facilities

Get in Touch

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